While many methods have been developed for high throughput screening of catalysts, not one of these previous apparatus or methods have provided the ability to test one catalyst or set of catalysts while simultaneously treating a different catalyst or set of catalysts with a different treat gas. In fast deactivating catalyst, the present invention significantly improves and reduces catalyst screening and optimization times. Although not as critical in stable catalysts with very long deactivation times, the apparatus and method of the present invention still could provide for improvements in catalyst screening and optimization.
In many industrially important reaction systems, the catalysts deactivate on a time scale that is shorter than or comparable to the reaction time scale. The present invention is designed for high-throughput evaluation of fast-deactivating catalysts such as those used in cracking of naphtha and gas oils, methanol to olefins processes, hydrocarbon dehydrogenation over noble metal catalysts, partial oxidation with metal oxides among many others. The deactivation is caused by such nonlimiting mechanisms as coking, fouling, poisoning, reduction or phase transformations among others. The time scales of deactivation range from milliseconds to minutes.
Previous high throughput catalyst systems are inadequate for fast deactivating catalysts because they cannot measure the catalyst performance in the reactor under the same time on stream (TOS), a prerequisite for comparing fast deactivating catalysts. Further, they are also inadequate in that fast-deactivating catalysts require pretreatment, regeneration, reactivation and reduction under proper conditions. This method is applicable to any standard definition of TOS, for example, clock time, weight of reactant processes per weight of catalyst, volume of reactant processed per volume of catalyst, gram of desired products produced per gram of catalyst, among many others. One of ordinary skill in the art would be familiar with other standard forms of TOS.
The patent literature abounds with high-throughput catalyst testing reactor designs. Many of these designs feature parallel reactors able to provide a common feed to the reactors sequentially or in parallel. Many previous inventions, for example U.S. Pat. No. 5,959,297 and WO 00/29844, present catalyst screening methods placing numerous small samples on a very thin substrate. While this method was adequate for stable catalysts, these methods were not suitable for fast deactivating catalysts as the samples were not tested at the same TOS. Also, these substrates do not allow for reaction at one substrate site while regeneration, reduction or some other processes occur at a second substrate site. Moreover, substrate designs would not allow for the careful individualized control of high temperatures and high pressures necessary for many catalytic systems.
Another problem of the above inventions is that they would not be effective for fast deactivating catalysts as their reactant recovery systems were not sensitive enough to recover sufficient product over very short exposure periods. WO 98/15969 solved this problem by proposing feed and recovery tubes that securely attached themselves sequentially to each element of the substrate. However, this invention still could not control the TOS and space velocity precisely enough necessary for fast-deactivating catalysts, nor would they have the ability for a second process to proceed on other substrate members.
U.S. Pat. No. 4,099,923 solved the high pressure and high temperature problems by sending a common feed to numerous parallel reactors. U.S. Pat. No. 6,149,882 developed a parallel reactor system that ensured the same flow rate through a catalyst by placing balancing flow restrictors between the common feed and the reactors and then sending the output to parallel detectors.
However, the '882 invention would not be effective for fast deactivating catalysts. With additional restrictions and balancing efforts, the TOS for each reactor could theoretically be controlled by using the '882 patent invention sequentially, as opposed to the parallel operations suggested. However, the device taught by the '882 invention still would not be useful for fast deactivating catalysts because the catalysts not actually being tested was not maintained in an initialized state (or individually optimized states) by a treatment gas other than the feed gas.
Although many high throughput catalysts screening systems have been developed, none of them would be effective for fast deactivating catalysts as they did not simultaneously control TOS and maintain the other catalysts in a ready condition to be tested. Further, these systems were inflexible even for stable catalysts in that they would not allow treatment of different catalysts in the parallel arrays by different feeds or treat streams.